Carbureter.



E. T. JOHNSON, W. H. GLASER & H. R. LLOYD.

GARBURETBR.

APPLICATION FILED MAR. 30, 1912.

1,974,625, V Patented Oct. 7,1913.

3 SHEETS-SHEET 2.

Patented 0011.7,1913.

3 SHEETS-SHEET 3 GARBURETER.

APPLICATION FILED MAR. 30, 1912.

E. T. JOHNSON, W. H. GLASER & H. R. LLOYD.

v f L pr m H 6 z 9 m m M A 0 0 1 PM. WW

To all whom it may concern:

UNITED STATES PATENT curios.

ERIC TOWNSEND JOHNSON, F TIMPERLEY, AND WILLIAM HENRY GLASER AND HAROLDBHYS LLOYD, OF CHEADLE HULME, ENGLAND.

GARBURETER.

Specification of Letters Patent.

Patented Get. 7, 1913.

Application filed March 30, 1912. Serial No. 687,298.

Be it known that we, E1210 TowNsnNn JOHNSON, a resident of Timperley,and WIL- LIAM HENRY GLASER and HAROLD RHYs LLOYD, residents of CheadleHulme, in the county of Chester, England, all subjects of the King ofGreat Britain, have invented new and useful Improvements in CarburetingApparatus, of which the following is a specification.

This invention relates to carburetors, principally for use with internalcombustion engines such as are employed for instance on automobiles.

The principal object of the invention is to provide a carbureter whichwill give automatically a constant or approximately constant mixture ofair and spirit throughout a wide range of speeds of flow of the air, 11.6. throughout a wide range of working speeds of the engine. .It may bedesirable to have a relatively rich mixture, 27. 6. one containing anexcessive amount of spirit in proportion to the air at low speeds, whileat higher speeds the mixture is of normal strength and is practicallyconstant in strength. Such a result is readily obtainable in accordancewith this invention in a carbureter which operates automatically Withoutthe use of any valves or like moving parts except such as are needed tomaintain an approximately constant amount of fuel in the feed chamber..This object is attained by the use of a contracting pipe of a kindsometimes called a Venturi pipe, through which the charges are drawn inby the engine, and in which the mixing or carbureting takes place. The.suggestion has been made already to use such a Venturi pipe in acarburetor with a spirit inlet at the narrowest section communicatingwith a float feed chamber, the spirit being forced out by the varyingpressure of the air on the surface of the spirit in the said chamber;this pressure was to be produced by having the float chamber closedexcept for a passage at its upper end communicating with apertures inthe Venturi pipe at or near-its largest section. It was then supthisformula :-a and p, are the area and posed that the pressure differencebetween .the air pressure apertures and the spirit in let aperture wouldbe proportional to the square of the quantity or speed of the airflowing through the ipe for any positions of the apertures, an that theamount of spirit forced through the jet would beproportional to thesquare root of the pressure lead, so that the feed of spirit would bedirectly proportional to the amount of air flowing through the pipe. AVenturi pipe was to be used having its sectional area at the narrowestpart about one eighth of the sectional area at the place where the airpressure openings are made. The above is mentioned in order todistinguish clearly from it the differences in theory and con-.struction on which the present invention is based. The said carbureterwould have operated correctly only if-air were an incompressible fluid,z. e. one which did not expand or contract with pressure changes, and ifthe air could be assumed to be at rest at the inlet of the pipe. Theseassumptions cannot be made, and in order to design a satisfactorycarburetor using a Venturi-pipe as above, it is necessary to take intoaccount the expansion of the air under reduction of pressure, and thedrop in pressure of the air at the inlet of the pipe. Itis alsoessential to insure substantially stream-line flow of the air throughthe pipe so that the rate of flow and the pressures may vary asrequired, and for this purpose a pipe must be used whose contraction ofsectional area from the inlet is such that the narrowest sectional areais not less than about 60 per cent. of the inlet area, while the pipecontracts gradually and approximately uniformly from the inlet to theneck.

In designing the carbureter use is made of the following formula whichcorrectly represents the relation betwen the area and pressure in a gasflowing through a ipe of gradually varying sectional area, neg ectingonly slight errors such as that due to friction, which is very small ina short pipe such as is used according to the present invention'. Theformula is g aar-taps F' "va a pressure respectively of the air at theinlet opening of the pipe, and a and 20, are the area and pressure atanother point in the pipe. 9 is the acceleration due to gravity, asusual. ris the ratio for air of the specific heat at constant pressureto the specific heat at constant volume. W represents the rate of flowof the air in units of mass per unit of time. V represents the volume ofunit mass of air at the pressure 12,. The method -of using this formulaand lts application to the design of a particular carbureter will now bedescribed with reference to the accompanying drawings, wherein Flgure 1is a diagram showing curves obtained from the above formula. Fig. 2 is asection of a carbureter according to the invention, having its pipevertical. Fig. 3 is a view partl in section, of the same carbureter seenrom the side. Fig. 4 is a plan View thereof. Figs. 5, 6 and 7 are detailviews showing sections of three different forms of horizontally arrangedcarburet'ers.

Fig. 8 is an enlarged sectional view of a supply chamber for the spiritorliquid fuel, and Fig. 9 is a partial face'view of a diaphragm used insaid chamber.

The procedure in designing a carbureter according to the invention is asfollows: The quantity W is estimated for the maximum speed of flow, thatis to say, the speed of flow when working with an engine at maximumspeed and with the throttle valve fully open. From this anarea a, ischosen for the pipe large enough to insure stream line flow of the air.A pressure p, is assumed (less than atmospheric pressure) and also 'apressure p not less than 70 per cent. of p, in order that stream lineflow may be insured. The assumed pressure 12, may be estimated byexperiment or calculation, but it is not necessary to determine it veryaccurately as the error due" to choosing p, slightly too large or toosmall is inappre ciable. The value of a, for the throat or neck of thepipe is next determined from the formula above, and also variousintermediate values of p, for intermediate values of a. After this thecalculations are repeated taking W for two thirds the maximum load andagain for one third the maximum load, assuming in each case su'itablevalues for p, which will be nearer to atmospheric pressure the lower thevelocity, and the corresponding value of W. The results so obtained areplotted on a diagram as in Fig. 1, in which vertical distances representpressures in pounds per square inch, and horizontal distances representdiameters of the contracting pipe. The curves then show the relationbetween the diameters of the pipe at various sections thereof, and thepressures atthose sections for each of the three selected speeds of flowof the air, which correspond a proximately to the maximum speed (whenthe engine is runnin at top speed) the normal speed, and the lowestordmary working speed respectively. The lowest curve in Flg. 1corresponds with the maximum speed and the highest curve correspondswith the lowest speed. The initial pressures 72, have been assumed asbeing.

13.7, 14 and 14.3 pounds per square inch for the maximum, normal andlowest speeds respectively, as the result of experiments, and the pipehas been chosen with a largest diameter of one inch. Having drawn thesecurves a pair of straight edges, designated by the lines K L and M N,are moved about in a vertical position over the curves until a positionis foundfor the lines in which a certain relation holds good; that is tosay, when horizontal lines are drawn from the points where the line M Ncuts the threecut the base line, and these are the desired pressureratios because they are proportional to the square of the differences inspeeds of flow of the air-through the pipe. If these pressuredifferences are used .in injecting the spirit at the oint of narrowersection (corresponding with'the position of M N) the amount of spiritinjected will be proportional to the air flowing, because the amount ofspirit which will flow through the orifice is proportional to the squareroot of the pressure under which it is forced to flow. The actual ratiosof A B: CD: E F are nearly 1.15: 4:92 in the diagram; this is adesirable departure from the exact proportions stated above because itwill result in a richer mixture being made at low speeds (as is desiredfor starting purposes for instance) and a slightly richer mixture atvery high speeds when maximum power is to be developed. The strength ofthe mixture is nearly constant for a wide range'of intermediate speeds.Thepoints where KL and M N cut the base line correspond with diametersof the pipe of 0.88 and 0.98 ofv an inch respectively. The smallestdiameter at the throat of the pipe may be about 0.78 of an inch withoutdisturbing the stream-line flow, if the angle of taper is small. Thediameter of the orifice through which the spirit is fed into the pipe isestimated from known data to be 1.375 millimeters to obtain In thedrawings, a carbureter is illustrated, designed as above explained.

tle valve which is fitted into the pipe 6- in the lower part thereof andis preferably formed to the same taper, as shown. it is a short cylinderor ferrule which may be fitted on the top of the carbureter pipe b, andwhich may be cylindrical in bore, the object of this ferrule being tosecure streamline flow in the air before it gets into the pipe 72itself. The pipe I) is one inch in diameter at the top where the line 70is marked -in diameter at the middle portion marked n whichmay becylindrical. From this point onward down the pipe the section increasesagain until it may be 1 inch at the bottom end 0. The pipe need notnecessarily be truly conical in the parts of varying section but it isshown so for convenience. Any suitable form of throttle may be used,butthe plug valve 9 is indicated as a convenient form of valve, aconical seating being turned out within the lower part of the pipe 6,and the plug 9 of conical form which fits in the seating being boredwith the tapering passage shown. The plug valve is held in place by astud and nut 72, and is adapted to be turned by means of a handle (whichis partially indicated) for the purpose of partly closing the passage inthe pipe I) and so reducing the flow of air therethrough. Theirregularity in the flow caused by the plug 9 in the-lower part of thepipe will notappreciably disturb the stream-line flow in the upper partabove the throat n so that the the flanges of the parts 0 and d, (seeFigs.

8 and 9) the said diaphragm being clrcumferentially corrugated so thatthe diaphragm will move laterally owing to differences of pressure atthe two sides thereofL. At the center of the diaphragm a boss 8 issecured, this boss being formedfor instance as a nut and a bolt screwingtogether to clamp the diaphragm between them. On one side of the boss 8is arranged a rod t with a tapered point acting as a needle valve in aseating a. This rod t iS=--arranged so as to follow the movement of'theboss 8. It may be at tached to the said boss in such a manner as not tointerfere with the free movement of the diaphragm but it is preferablymounted so as to be pressed by a spring-against a tapering point on theboss 8. In the arrangement illustrated in the drawings a small collar isformed on the end of the rod t adjacent to the boss .9 and a groove isformed infront of this collar. In this groove engages the forked end ofa strip spring t which is mounted on the member 0 and presses againstthe collar on the rod t so as to cause this rod to follow the movementof the'diaphra-gm s away from the seating u. The pipe conveying theliquid fuel to the carbureter is shown at 0 opening into the valveseating u. From the seating u a branch passage w leads into the chamberin the member c, and there is a suitable cock :0 1n the branch passage,this cock being normally set to close the passage and being opened onlyfor instance when it is required to fill the carbureter chamber instarting working therewith or after emptying the same- At the top of thediaphagm 1' holes are formed to allow the air pressure to be equalizedat both sides of the diaphragm and-also to allow for the flow of theliquid fuel at a certain level. In Fig. 9 two holes 11 are shown for theflow of the liquid, and another hole 10 at a higher level which willinsure the equalization of the air pressures. A duct 3/ (referred tohereinbefore as the air pressure duct) formed in the projecting sideportion of the carbureter pipe leads from the top of the diaphragmchamber at the right-hand side thereof as seen in Fig. 2 up to anorifice in the carbureter pipe I) at the line Z where the diameter inthe pipe is .98 of an inch. Another passage 2 leads from a point nearthe bottom ofthe diaphragm chamber at the right-hand Side thereof asseen in dotted lines in Fig. 2 up to the interior of the projection f,in which is a ferrule 2' fitted in a bore in the projection f, and heldagainst a seating at the inner end thereof by means of a screw plug 12.The

ferrule 71 has a central orifice, which is on the line m as seen in Fig.2, and a hole at 13 communicating with the passage 2 so that the liquidfuel forced out from the diaphragm chamber 0" through the passage .2 canreach the interior of the ferrule 2', and can enter the pipe 6 from thesmall orifice at the inner end of the said ferrule.

The working of this carbureter will now be evident with very littlefurther explanation. Assuming the diaphragm chamber to be empty at bothsides of the diaphragm the plug valve 00 will be turned to admit alittle liquid fuel into the chamber at the left-hand side of thediaphragm (Fig. 2) and then as the chamber fills the diaphragm 7' willbecome pressed back causing the needle 'the right-hand side toapproximately the level indicated in Fig. 2, and the parts are at theright-hand side falls again, thu upsetting the balance of pressure andcausing the needle valve t to open. The level of the liquid'at therlght-hand or outlet side of the diaphragm will not'in practice varygreatly because directly thelevel begins to sink the valve will open andmore liquid will be admitted which. will overflow to the outlet side ofthe diaphragm. The device then serves to maintain the liquid at anapproximately constant level in the chamber communicating with the fuelinlet orifice in the member '5. This orifice is a little way above thelevel of the liquid so that there is no risk that the liquid will floodthe passage leading to the orifice, and escape. When the engine isdrawing in a charge however there will be the differences of airpressure produced between the opening of the air pressure duct y and thefuel orifice in the member 71, and the increased pressure on the surfaceof the liquid in the diaphragm chamber will cause the liquid to beejected through the passage 2 and ferrule a into the carbureter pipe I),the amount of liquid injected varying with the amount of air flowingthrough the pipe in the manner already explained; The little differencein pressure due to the fact that the orifice of the ferrule 71 is abovethe level of the liquid in the diaphragm .chamber will make noappreciable difference to the amount of the liquid fuel injected throughthe said orifice. The variations in the air pressure in the diaphragmchamber at different speeds of flow of the air through the carburetorpipe will be communicated equally to both sides of the diaphragm 1- sothat they will have no effect on the said diaphragm, and will not causethevalve t to open and close. The opening of the said valve will dependtherefore solely upon the falling of the level of the liquid at theoutlet side of the diaphragm. The throttle valve 9 will be used in thewell known way to reduce the supply of carbure'ted air when the engineis running fast, and when the full power is not required, and then ofcourse the amount of air passing through the pipe will be reduced,but-the carbureter will always work under normal circumstances withinthe ranges of speed of air for which it was designed.

The construction of the carbureter can of course be varied considerablybut the arrangement shown in Figs. 2, 3 and 4 indicates the experimentalform -of the carbureter. The carbureter pipe I) need not necessarily bevertical although that will be the most convenient position of the pipefor many types of engines. The pipe 6 may be horizontal if preferred orin any other po- .sition, and of course its section will be the same forworking with the same engine, no matter what its position. In a verticalpipe the parts may be suitably transposed to allow the air to flow in anupward instead of a downward direction.

Fig. 5 shows a section through a horizontal carbureter pipe b taken onthe line at where the fuel inlet orifice is. The parts 0 and d includingthe diaphragm chamber and inlet valve may be the same as in theconstruction already described; the ferrule '5 in which is formed thefuel inlet orifice is shown as being arranged vertically and openinginto the carbureter pipe at the lower end of the vertical diameterthereof. This view will'require no further explanation and it will beobvious that the carbureter will work in this case in precisely the samemanner as the carbureter shown in Figs. 2, 3, and 4. The air pressureduct s not indicated in Fig. 5 but of course it communicates with thecarbureter pipe at a point of larger section and leads into thediaphragm chamber above the level of the liquid just as in Fig. 2.

Fig. 6 shows a type of fuel inlet orifice as applied to ahorizontal'carbureter pipe, this orifice having a crew plug 15 formedwith a conical head 16 adjustable in the said orifice 17 in the pipe I).The object of this construction is to enable the fuel inlet orifice tobe adjusted when required. A look nut 18 secures the plug 15 in theposition in which it is set.

In Fig. 7 a tapered plug valve 19 is shown forming an adjustable fuelinlet valve. The tapered plug 19 i held in place register wholly orpartially with the orifice 21 leading into the carbureter pipe I). Inthis way the size of the orifice can be adjusted. Of course it is notintended that the adjustable valve should be altered in its settingduring normal working but it would be altered if the feed of fuel wasfound to be too low or too high, and then the automatic \variations inthe fuel supply with difierent amounts of air flowing through thecarbureter pipe would insure the correct proportionality between thefuel and air at the different speeds of the en 'ne. 7

Various modifications in t e apparatus can be made without departingfrom the scope of the invention. For instance the diaphragm feed devicemay be replaced by any known equivalent device for maintaining thespirit at a constant level in the feed chamber. Further, any otherarrangement for filling the said chamber with spirit at nearer to oreven it may be at the throat nof the pipe when designed for certainamounts of air and ranges of speeds as hereinbefore explained. It ispreferable however, to have a throat in the pipe beyond the spirit inletorifice as shown, so that there will be a reduction of pressure withconsequent further expansion in passing through the throat n,.which willassist in the vaporization of the spirit. The throat also protects thecarbureter against the efiects of resurgence due to sudden pressurechanges in the pipe leading to the engine. lhe direction of flow oftheair through the carbureter pipe might be reversed, as the pressuredifferences would still be practically the same for the same speeds offlow. .The

pipe need not vary uniformly in section, but

anydesired form of pipe of varying section may be used, provided thatthere is no sudden change of section such as would be likely to produceeddies in the air.

The invention is evidently applicable for mixing any readily vaporizable liquid with a gas, and the word air may be read throughout ascovering also other gases than air, while spirit or liquid fuel coversany readily vaporizable liquid to be mixed with the gas. Similarly theword carbureter may be read as including a mixing apparatus of thetypedescribed, for. a gas and a vaporizable liquid, used for any suit; ablepurpose.

We claim as our inventions-- 1. In a carbureting apparatus, the combi--nation of a pipe of gradually varying section with two openings theremat points of different section, the said sections being of areas suchthat the fluid pressure differences between said openings caused by 'theflow of air through the pipe at varying speeds and the correspondingvarying pressures at,

the two openings are substantially proportional to the square of thequantity of air flowing at the various speeds, connecting passagesbetween said openings and means for supplying spirit to one of thepassages under a gaseous pressure head determined by the other passage.

2. In a carbureting apparatus, the combination of a pipe of graduallyvarying section with two openings therein at points of differentsection, the said sections being of areas such that the fluid pressuredifferences between said openings caused by the flow of air through thepipe at varying speeds, and the corresponding varying pressures at thetwo openings are substantially proportional to the square of thequantity of air flowing at the various speeds, a chamber and means ofsupplying spirit thereto, a passage leading from the opening at thelarger section of the pipe to the upper part of said chamber,

and another passage leading from below the level of the spirit in saidchamber to the opening in the pipe at the smaller section thereof.

3. In a carbureting apparatus, the combination of a pipe of graduallyvarying section formed with an .intermediate throat whose free sectionalarea is more than sixty per cent. of the sectional area at the inlet ofthe pipe, said pipe having two apertures, one at a point of largersection and the other at a pointof smaller section, connect-ing passagesbetween said apertures, and means for supplying spirit to one of saidpassages under a gaseous. pressure head determined by the other passage.

4. In a carbureting apparatus, the combination of a pipe of graduallyvarying section contracting from the inlet end to a throat whose freesectional area is more than sixty per cent. of the sectional area at theinlet, said pipe being formed with two apertures at points of diflerentsectional area, both at the side of the throat at which the inlet lies,connecting passages between said apertures, and means for supplyingspirit to one of said passages under a gas eous pressure head determinedby the other passage.

,, In witness whereof, we have hereunto signed our names this 22nd dayof March 1912, in the presence of two subscribing witnesses.

. Witnesses to allthe signatures: ERNOLD SIMPSON MOSELEY, MALCOLMSMn-THURs'r.

